In the first trial of its kind across the world, the City of Sydney has put its new blend of environmentally friendly concrete to the test, created with a combination of industrial waste from coal-fired power stations and steel manufacturing.

Working with researchers from the University of NSW, the City of Sydney replaced a section of roadway on Wyndham Street in Alexandria to test the green concrete’s durability.

Made from fly ash and blast furnace slag, geopolymer concrete is a sustainable blend of concrete and recycled materials.

Geopolymer generates just 300kgs of CO2 per tonne of cement, compared to 900kgs from traditional cement production. The carbon emissions savings is equivalent to the electricity used by an average household every 2 weeks.

With 70 percent of the concrete produced today going into pavements and footpaths, using products like geopolymer concrete for our roads and footpaths has great potential to further lower emissions from our operations.

As a major road leading to Sydney Airport, Wyndham Street’s high traffic volume provides the perfect conditions for the trial.

Nine sensors have been positioned under the concrete to monitor and compare how the geopolymer concrete performs.

University of NSW researchers and the Cooperative Research Centre for Low Carbon Living will use results from the trial to create the first set of industry guidelines for geopolymer concrete.

Research has been undertaken since the 1990s, but it’s only now this concrete blend is being explored as a product that is not only better for the environment, but also commercially viable.

The low CO2 concrete has the potential to put the 400 million cubic tonnes of globally documented waste from the coal and steel industries to good use. While a small amount is currently used in construction, much of it is currently stored onsite.

University of NSW researchers will monitor the road performance for up to 5 years.

Professor Stephen Foster, head of school of civil and environmental engineering, is the project lead. He describes the trial as “a huge step forward”.

“This trial will help drive step-change in the industry. Many concrete companies are already doing a lot to change, but this trial really gives it another push,” Foster said. “While we’ll monitor the road performance for up to five years, a lot of the data collected in the first three to 12 months of this world-first trial will be used to confirm our models and strengthen our predictions.

“Concrete contributes seven percent of all greenhouse gas emissions and in 2018 the world produced about 4.1 billion tonnes of cement, which contributed about 3.5 billion tonnes of CO2. Alternative, low CO2 concrete materials offer potential benefits in reducing the greenhouse gas emissions associated with conventional concrete. This trial is important because we need demonstration projects to accurately assess the performance of geopolymer over time so that there can be broader uptake.”